Center opt in form in widget

Good morning,

I am having trouble with the form showing up on my customers webpage. I am using the Spacious theme that allows me to place the webform in my header, so I have. It shows up on my page but it appears to be aligned to the right and I dont know how to change it. I want it centered.

Im using form #1, here is a link to the webpage.

http://www.gumballlove.com/

Please help.

https://wordpress.org/plugins/optin-forms/